Conventionally, reflective liquid crystal displays have been constructed using a pair of polarizers, a reflective layer placed on the outside of one of the polarizers, and a TN (twisted nematic) or STN (super twisted nematic) liquid crystal device sandwiched between them. This configuration, however, has the problem that not only is the low brightness of the display, but shadows appear on the display because the reflective layer is placed outside the glass substrate.
To address this problem, there has been proposed a single-polarizer reflective liquid crystal display that can produce a display using a single polarizer. Since only one polarizer is used, the brightness can be improved compared with the conventional reflective liquid crystal display that uses two polarizers.
In the case of the single-polarizer liquid crystal display, the display shadow problem can also be solved by forming a reflective layer within the liquid crystal display device.
The single-polarizer liquid crystal display comprises a single polarizer, a single retardation film, and a liquid crystal device incorporating therein a reflective layer; this type of display is disclosed, for example, in Japanese Unexamined Patent Publication No. 4-97121. Another type of single-polarizer liquid crystal display has also been proposed which uses, instead of the retardation film, a compensation layer having a twisted structure whose twist direction is opposite to that of the liquid crystal layer; this type of display is disclosed, for example, in Japanese Unexamined Patent Publication No. 10-123505.
However, in the case of the single-polarizer liquid crystal display that uses a single polarizer and contains a reflective layer within the liquid crystal device, if the reflective layer is a specular reflector, since incident light is not reflected in any direction other than the specular direction, display brightness is reduced. To address this, in one method it has been practiced to roughen the reflective electrode in order to enhance display brightness in other directions than the specular direction, but the problem is that this requires a difficult manufacturing process.
To achieve a bright display with a simpler construction, a liquid crystal display has been developed that uses a specular reflector and that includes on the outside of the polarizer a scattering layer that exhibits large forward scattering but small back scattering; this type of display is disclosed, for example, in Japanese Unexamined Patent Publication No. 8-201802.
However, in the liquid crystal display provided with such a scattering layer, image blurring occurs if the degree of scattering of the scattering layer is raised to enhance brightness; as a result, it has not been possible to raise the degree of scattering satisfactorily, and there has been a need for a display with enhanced brightness.
To achieve a brighter display, a liquid crystal display has been developed that uses a specular reflector and that includes a plurality of scattering layers on the outside of the polarizer or between the liquid crystal device and the polarizer, the incident angle dependence of scattering of at least one of the scattering layers being made asymmetrical about the layer normal; this type of display is disclosed, for example, in Japanese Unexamined Patent Publication No. 11-119215.
With this liquid crystal display, since the degree of scattering is reduced in the viewing direction and increased in the incidence direction by using a scattering layer whose angle dependence of light scattering is asymmetrical about the layer normal, a bright display can be obtained while reducing image blurring to a relatively small level. However, increasing the degree of scattering in the incidence direction has had the disadvantage of reducing the contrast because the back scattering of the incident light increases. A further disadvantage has been that since the angular dependence of scattering of the incident light is large, the brightness changes abruptly, resulting in degradation of the viewing angle characteristic.
An object of the present invention is to solve the above-enumerated problems and provide a single-polarizer liquid crystal display that can achieve, with a relatively simple construction, a bright display with reduced image blurring over a wide viewing angle range.